I am building a custom, soundproof door out of two layers of 3/4" MDF. It's not as rigid as I'd like it to be and has a bit of bow to it which will eventually compromise the neoprene seal that I will be installing around the stop.

What I need is a low-profile method of reinforcing this door and Menard's seems to have what I need, a 1 1/2"x1/8"x6' steel strip. It is very rigid and will definitely keep the door from warping or bowing. My initial idea was to fix this strip to the inside edge of the door and drill a 1" hold through it for the door handle's latch bolt. Someone else on this site brought up several complications in that method, so it may not work.

However, I still want to use the metal strip for reinforcement. If I could find a door knob/handle that has the latch on the outside, I wouldn't have to worry about drilling a hole through steel. Does such a thing exists and, if so, what do you call such an assembly as this?

I know they make them for commercial/walk-in freezers, so yes they exist.
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JasonMar 21 '13 at 15:53

Does it need to latch? Could you get away with false knobs (surface mount) and a bunch of magnets on the jamb up against the steel?
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Chris CudmoreMar 21 '13 at 17:03

I like the idea of magnets, but I don't know if they would give me the tight seal I need against the neoprene seal that will eventually be installed. In fact, the seal would not allow any room for magnets, I don't think. I want a latch because this would allow me to pull the door tight against the seal and have it latch tight in place. So far, one answerer suggested rim locks and I am thinking this is what I've been looking for all along.
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oscilatingcretinMar 21 '13 at 17:56

+1 the house I grew up in had one of these on the front door, but I never knew the name.
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BMitch♦Mar 21 '13 at 16:01

I think you have delivered the solution I am looking for! I knew I could count on SE. I will let you know as soon as I am done researching. It looks like these are all special order items and not available in stores.
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oscilatingcretinMar 21 '13 at 17:14

Going off my comment earlier, one example would be a Walk-in Safety Latch. The specification of a safety latch is

Where there is a possibility of entrapment within a latched enclosure,
safety standards require the use of a latch or handle fitted with an
inside release mechanism. Latches without this feature are intended
for use only on small units or units with insufficient space for
entrapment.

I guess the steel strip is on the far side (away from hinges) mounted vertically along the edge.

Right?

Then I'm not really sure what you mean by "latch on the outside?" What kind of latch?

If you mean "latches on the other side of the door, where I can't access it" then something like an automatic gate hinge might work.

I've often seen people put this on the far-side/back/"out-side" of a gate, and tie a little piece of string through that eyelet. Pulling the string from the "inside" opens the latch and lets you pull the door open.
To get the string to your side of the door, you would have to drill a little hole, though, and that might compromise your sound proofing a little.
Also, don't ever let the string break.

However, I'm still wondering why you can't mount your steel strip 6" from the edge, and save yourself all of this hassle?

The actual latch bolt is what I am referring to. When you turn the handle, the latch retracts inward to pull away from the strike plate. A 1" hole has to be drilled into edge of the door for this piece. I am wondering if a handle exists where the equivalent of a latch bolt is mounted on the front or back of the door, yet still be accessible from both sides. As far as why I can't put it 6" from the edge is because the strip is not rigid along its flat side which is only 1/8" which will just cause the strip to bow along with the door.
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oscilatingcretinMar 21 '13 at 15:24